1. Field of the Invention
The present invention relates to an apparatus for reducing the failure rate of automobile airbags. More particularly, the present invention relates to an apparatus for reinforcing an airbag to prevent damage to the airbag when deployed through the airbag cover.
2. Technical Background
Inflatable airbags are well accepted in their use in motor vehicles and have been credited with preventing numerous deaths and accidents. Some statistics estimate that frontal airbags reduce fatalities in head-on collisions by 25% among drivers using seat belts and by more than 30% among unbelted drivers. Statistics further suggest that with a combination of seat belt and airbag, serious chest injuries in frontal collisions can be reduced by 65% and serious head injuries by up to 75%. Thus, airbag use presents clear benefits.
In view of the apparent success of airbags, automobile designers and the consuming public have been anxious to increase the number of airbags present in vehicles. Currently most automobiles being manufactured have driver side and passenger side airbags. However, designers are identifying increasingly more locations to place airbags throughout the vehicle. For example, side impact airbags and overhead inflatable curtains are becoming more and more common in vehicles. These airbags prevent injury that might occur in side-impact collisions. Other airbag designs have been created to protect less obvious portions of the body, such as the knee.
In order to place multiple airbags throughout an automobile, designers have sought after ways of reducing the storage size of airbags. One, method of reducing the storage size of an airbag is to decrease the thickness of the airbag material. By decreasing the thickness of the airbag material the inflated volume of the airbag will remain the same, but the undeployed airbag storage volume will be reduced.
Reducing the thickness of the airbag also has the added advantage of limiting the force in which an airbag “impacts” an occupant. As an airbag deploys and first comes in to contact with the occupant, the airbag might slap the occupant it is about to restrain. The force of the slap is generally equal to the mass of the airbag multiplied by the acceleration of the airbag. Reducing the mass of the airbag by decreasing the thickness will correspondingly decrease the force of the deploying airbag. Thus reducing the mass of the airbag provides additional safety features.
However, decreasing the thickness of an airbag can have some negative effects on the airbag module. One negative effect is that thinner material is generally weaker than thicker material. Testing of the new design of an airbag using light weight airbag material was found to have failures while breaking through the tear seams of the airbag cover. The testing revealed that aneurysm type failures were developing in the airbag as the airbag broke through the tear seams of the airbag cover.
Various airbags were tested in these experiments, such as a double section accordion type airbag. A double section airbag is comprised of two individual accordion shaped sections that create a fold seam between the two folded sections. This folded configuration produces inflation results that are desirable in some applications. The testing of this airbag revealed that the interaction between the fold seam of the airbag and the orientation of the tear seams were a factor in producing these failures.
The testing revealed that when the fold seam of the double section accordion type airbag was perpendicular to the orientation of the tears seam, failures in the airbag occurred. These failure locations matched the orientation of the tear seam. Conversely, it was noted that when the orientation of the airbag fold seam was parallel to the tear seam, no failures occurred. Testing suggests that the parallel alignment of the fold seam and the tear seam produce few, if any, failures because the parallel alignment allowed for even distribution of the airbag on the airbag cover. On the other hand, the perpendicular alignment concentrated areas of high force and stress on small portions of the airbag, thus causing the aneurysm type failures.
These areas of high force and stress are believed to be created as the airbag impacts the airbag cover and as portions of the airbag deploy through the airbag cover. The impact of the airbag on the back of the airbag cover creates high stress points along various contours of the airbag cover. These forces and stresses can cause failures in the airbag, especially along the contours that create the tear seam.
Additionally, high stress concentrations may occur in the airbag when the tear seam initially opens releasing only a small section of the airbag. As small sections of the airbag bubble out of the airbag cover, areas of high stress are created in the bubbled out sections of airbag. Furthermore, if the edges of the airbag cover are rough, then these rough edges might rub against the airbag as it deploys, causing holes and tears in the airbag.
While these failures occurring in the airbags were substantially corrected by parallel alignment of the fold seam and the tear seam, certain airbag applications prohibit a parallel alignment. In various airbag applications, the fold seam of the airbag must be oriented perpendicular to the tear seam of the airbag cover. Thus, the problem remains of reinforcing a thinner gauge airbag having a perpendicular alignment.
Therefore, what is needed in the art is an airbag apparatus capable of a perpendicular alignment of the fold seam to the tear seam that implements a thinner gauge of airbag material. What is further needed is an airbag structure capable of distributing forces and stresses induced by opening an airbag cover. A need also exists for reinforcing an airbag as small sections of the airbag bubble out of a partially opened tear seam.
What is further needed is a cover deployment member to limit the contact between the airbag and the airbag cover. A need also exists to provide a cover deployment member that may be easily implemented and interchangeable in multiple folded airbag configurations. Another need exists for reinforcing various airbag designs with little additional part and assembly costs. What is further needed is an apparatus to reinforce an airbag having a fold seam perpendicular to the tear seam during deployment through an airbag cover.